Subsea production cooler

ABSTRACT

A subsea production cooler module comprising: a core; a coiled tubing disposed around the core, wherein the coiled tubing comprises an inlet and an outlet; and a shroud at least partially encasing the core and the coiled tubing.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/831,880, filed Jun. 6, 2013, which is incorporated herein byreference.

BACKGROUND

The present disclosure relates generally to subsea production coolers.More specifically, in certain embodiments the present disclosure relatesto subsea production coolers that utilize natural convection andassociated methods.

Crude oil and other fluids produced from production wells are sometimesproduced at temperatures too high for handling by available subseahardware, for example at temperatures at or above 400° F. These hightemperatures may create a thermal strain on hardware on the seafloor andoften may require additional cooling of the fluid on the topsides. As aresult, it is desirable to cool these fluids to temperatures in therange of 180° F. to 300° F. before they are transported along or fromthe seafloor.

Conventional subsea cooling techniques utilize un-insulated productionpiping arranged in sets of hairpin turns or other configurations such asa pyramid convecting freely to the surroundings. Typically, theseconventional subsea cooling techniques have very limited ability toadapt to changing flow rates or temperatures of the produced fluids.This may result in excessive cooling, which may be problematic in fluidsthat are not fully inhibited against hydrate blockage by chemicals.

It is desirable to develop a method of subsea cooling that provides ameans of reliable cooling with an ability to adapt to changing flowrates and temperatures. It is also desirable to develop a method ofsubsea cooling that uses sea water at 40° F., with consideration givento excessive cooling and unacceptably cold piping surface temperatures.

SUMMARY

The present disclosure relates generally to subsea production coolers.More specifically, in certain embodiments the present disclosure relatesto subsea production coolers that utilize natural convection andassociated methods.

In one embodiment, the present disclosure provides a subsea productioncooler module comprising: a core; a coiled tubing disposed around thecore, wherein the coiled tubing comprises an inlet and an outlet; and ashroud at least partially encasing the core and the coiled tubing.

In another embodiment, the present disclosure provides a subseaproduction cooler comprising: a subsea production cooler modulecomprising: a core; a coiled tubing disposed around the core, whereinthe coiled tubing comprises an inlet and an outlet; and a shroud atleast partially encasing the core and the coiled tubing; a base; and apiping system.

In another embodiment, the present disclosure provides a method ofcooling a subsea production stream comprising: providing a subseaproduction stream and cooling the subsea production stream with a subseaproduction cooler module, wherein the subsea production cooler modulecomprises: a core; a coiled tubing disposed around the core, wherein thecoiled tubing comprises an inlet and an outlet; and a shroud at leastpartially encasing the core and the coiled tubing.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete and thorough understanding of the present embodimentsand advantages thereof may be acquired by referring to the followingdescription taken in conjunction with the accompanying drawings.

FIGS. 1A and 1B are illustrations of a subsea production cooler modulein accordance with certain embodiments of the present disclosure.

FIG. 2 is an illustration of a subsea production cooler module inaccordance with certain embodiments of the present disclosure.

FIG. 3 is an illustration of a subsea production cooler module inaccordance with certain embodiments of the present disclosure.

FIG. 4 is an illustration of a subsea production cooler in accordancewith certain embodiments of the present disclosure.

The features and advantages of the present disclosure will be readilyapparent to those skilled in the art. While numerous changes may be madeby those skilled in the art, such changes are within the spirit of thedisclosure.

DETAILED DESCRIPTION

The description that follows includes exemplary apparatuses, methods,techniques, and instruction sequences that embody techniques of theinventive subject matter. However, it is understood that the describedembodiments may be practiced without these specific details.

In certain embodiments, the present disclosure relates to techniques forcooling production fluids produced from subsea wells. Such cooling mayinvolve utilizing natural convection. In certain embodiments, thecooling may be accomplished without using pumps to circulate theproduction fluids or cooling fluid within the subsea production coolers.

Produced fluid exiting a wellhead on an ocean floor may flow through aseries of coils in a production cooler where it is cooled by cold seawater or other cooling fluid. The cold sea water or other cooling fluidmay be heated by the coils, become less dense, and rise away from thecoils due to natural convection. As the heated sea water or othercooling fluid rises away it may be replaced by colder, denser seawaterfrom the surrounding area in a continuous flow or by cooled coolingfluid. Because the flow of the produced fluid through the coils may bedue to well pressure and the flow of seawater or other cooling fluid maybe driven by buoyancy, in certain embodiments the pumping of fluids isnot be required.

Some desirable attributes of the subsea production coolers discussedherein may include: predictable performance for both design andoperational monitoring; the ability to adjust heat transfer to maintaindesired outlet temperature; the ability to tolerate changes inproduction flow rate and maintain desired outlet temperature; a cooldown time similar to the insulated flowline system; robust pipingcapable of withstanding multiphase flow; functionality to distributemultiphase flow and produce even cooling; by-passable; minimization ofboth internal and external fouling; the ability to maintain interiorwall temperature greater than the wax deposition temperature (e.g. 110°F. at all times); the ability to maintain exterior wall temperature lessthan the seawater scale formation temperature (e.g. 130° F. at alltimes); the ability to allow sea water side cleaning by remotelyoperated vehicles, and the ability to control circulation of the seawater to meeting cooling demand.

Referring now to FIG. 1, FIG. 1 illustrates a subsea production coolermodule 101 in accordance with certain embodiments of the presentdisclosure. In certain embodiments, subsea production cooler module 101may comprise a core 110, coiled tubing 120, shroud 130, and a controlvalve 140.

In certain embodiments, core 110 may generally have a cylindrical shape.Core 110 may be sized to efficiently cool a variety of productiontemperatures and flow rates. In certain embodiments, core 110 may befrom 3 feet to 15 feet in diameter and/or from 10 feet to about 100 feetin height. Core 110 may be constructed out of any material suitable forin a deepwater environment. Examples of suitable materials includesteel, glass reinforced plastic, and/or a variety of compositematerials. In certain embodiments, an outside surface 111 of core 110may comprise a coating 112. Examples of suitable coating materialsinclude solid glass reinforced plastics, epoxy coatings, specializedpaints, and insulating materials. Coating 112 may be structural,semi-structural, or non-structural in order to achieve a desired shape,geometry, or surface characteristic. In certain embodiments, thethickness of coating 112 may be determined by its desired properties. Incertain embodiments, coating 112 may be from about 0.005 inches thick to0.020 inches thick. In other embodiments, coating 112 may be from aboutfrom 0.1 inches thick to 0.4 inches thick. In other embodiments, coating112 may be from 0.02 inches thick to 0.05 inches thick. In certainembodiments, coating 112 may prevent the warmed cooling fluid retainedin subsea production cooler module 101 from rapidly cooling duringunexpected shutdowns. In certain embodiments, core 110 may have a hollowcenter. In other embodiments, the subsea production cooler module 101may have no core.

In certain embodiments, coiled tubing 120 may comprise any suitabletubing material in a coil formation. In certain embodiments, coiledtubing 120 may comprise a single coil of tubing or multiple coils oftubing. For example, coiled tubing 120 may comprise one, two, three,four, or five or more individual coils of tubing. In certainembodiments, each individual coil of tubing may have its own inlet andoutlet. When subsea production cooler module 101 comprises a core 110,coiled tubing 120 may be coiled around core 110. In embodiments wheresubsea production cooler module 101 does not comprise a core 110, coiledtubing 120 may define a cavity.

In certain embodiments, coiled tubing 120 may have a coil geometrycomprising one or more inner coils and one or more outer coils. Incertain embodiments, the one or more inner coils may be disposed aroundcore 110 and the one or more outer coils may be disposed around the oneor more inner coils. In certain embodiments, the inner and outer coilsmay be spiraled in the same direction. In other embodiments, the innerand outer coils may be spiraled in opposite directions. In embodimentswhere the inner and outer coils are spiraled in opposite directions,torsion present in the inner and out outer coil in coiled tubing 120 maybe arranged to balance each other, which may in turn decrease theoverall structural strength required to manage the force and movement ofcoiled tubing 120 under production pressures and temperatures.

In certain embodiments, the geometry of coiled tubing 120 may maximizethe beneficial effect of creating flow through two independent, butcomplimentary effects. First, by having multiple individual coils oftubing transferring heat to the same fluid multiplies the temperaturerise and the subsequent coolant buoyancy that creates the naturalconvection heat transfer. Second, by placing the coils in closeproximity to each other and the surfaces of core 110 and/or shroud 130,there may be an additional enhancement of heat transfer at certainoperating conditions due to fluid flow effects. For example, in certainembodiments, the coils may be spaced about core 110 such that thedistance between the center of coiled tubing 120 in each coil is from1.5 to 2 times the diameter of coiled tubing 120.

In certain embodiments, the geometry of coiled tubing 120 may allow theavoidance of sudden turns that occur in standard elbows or hairpinturns, reducing the localized accumulation of solids on the interiorwall of coiled tubing 120 through enhanced deposition that is believedto be due to low velocity areas created in the fluid stream by theturning actions and the cold spots that can occur due to the non-uniformflow field.

Coiled tubing 120 may be constructed out of any suitable tubingmaterial. Examples of suitable tubing materials comprise carbon steel,stainless steel, titanium, nickel alloys, and composite materials. Incertain embodiments, the composite materials may comprise differentmaterials arranged to give certain beneficial properties to the surfacesof the coil 120 that may be different than the properties of the bulk ofthe tube wall. In certain embodiments, coiled tubing 120 may comprise aninner diameter of from one inch to six inches.

In certain embodiments, an inner surface 121 of coiled tubing 120 maycomprise an inner coating 122. Inner surface 121 may be completely orpartially coated with inner coating 122. In certain embodiments, innercoating 122 may comprise ceramic enamel or a diamond-like coating. Incertain embodiments, inner coating 122 may be from 2 to 30 micronsthick. In other embodiments, inner coating 122 may be from 5 to 10microns thick.

In certain embodiments, an outer surface 123 of coiled tubing 120 maycomprise an outer coating 124. Outer surface 123 may be completely orpartially coated with outer coating 124. In certain embodiments, outercoating 124 may comprise ceramic enamel, ethylene copolymer such asHalar, a thermoset polymer, a diamond-like coating, or a phenoliccoating. In certain embodiments, outer 124 coating may be from 2 micronsthick to 400 microns thick. In other embodiments, outer coating 124 maybe from 10 microns thick to 50 microns thick.

The selection of material and thickness for coiling tubing 120 may becritical in controlling the surface temperatures both on the inside andthe outside of coiled tubing 120. In certain embodiments, it may bedesirable to keep the coil surface temperatures in safe limits bydesigning the appropriate fluid velocities and heat transfercoefficients. In certain embodiments, the temperature of inner surface121 or inner coating 122 of coiled tubing 120, as appropriate, should bemaintained above a minimum value because of the concern of wax deposits.In certain embodiments, the temperature of inner surface 121 or innercoating 122 of coiled tubing 120 should be maintained at a temperaturegreater than 110° F. In certain embodiments, the temperature of outersurface 123 or outer coating 124 of coiled tubing 120, as appropriate,should be maintained below a maximum value because of concerns withcorrosion and sea water scaling. In certain embodiments, the temperatureof outer surface 123 or outer coating 124 of coiled tubing 120, asappropriate, should be maintained at a temperature less than 150° F. Inother embodiments, the temperature of outer surface 123 or outer coating124 of coiled tubing 120, as appropriate, should be maintained at atemperature less than 130° F.

In certain embodiments, coiled tubing 120 may comprise an inlet 125 andan outlet 126. In certain embodiments, inlet 125 may be located near thebottom of core 110 and outlet 126 may be located near the top of core110. Inlet 125 may be connected to a hot production fluid line 127.Outlet 126 may be connected to a vertical discharge line 128. In certainembodiments, hot production fluid line 127 and/or vertical dischargeline 128 may disposed within a hollow center of core 110. In otherembodiments, hot production fluid line 127 and/or vertical dischargeline 128 may be disposed within the cavity defined by coiled tubing 120.In other embodiments, hot production fluid line 127 and/or verticaldischarge line 128 may be disposed on an outside surface 111 of core110.

In certain embodiments, coiled tubing 120 may comprise one or morebypass lines 129 allowing the fluid to short circuit the productionfluid path to the outlet 126, and allow production fluid to flow intothe vertical discharge line 128. In certain embodiments, bypass line 129may have a valve 160 installed to manage the volume of flow directedthrough bypass line 129.

During operation, a production fluid may flow into the subsea productioncooler module 101 through hot production fluid line 127, through thecoiled tubing 120 where it is cooled, and out of the subsea productioncooler module 101 through vertical discharge line 128. The flowrate ofthe production fluid entering the subsea production cooler module 101may be determined by the particular production well supplying theproduction fluid to subsea production cooler module 101. This flowratevary considerably, particularly during conditions when the productionwell is brought back online after being shut off.

The production rates that the subsea production cooler module 101 mayefficiently cool to desired outlet temperatures may be in the range from2000 barrels/day to 50,000 barrels/day. Any number of combinations offlowrate, pressure, temperature, fluid thermodynamic state, andcompositional details may exist at the inlet 125 and outlet 126 ofsubsea production cooler module 101. This possible variation of manyoperating parameters is well known to those skilled in the art. Incertain embodiments, the production fluid entering the subsea productioncooler may be at a temperature of from 250° F. to 450° F. In certainembodiments, production fluid leaving the subsea production coolermodule may at a temperature of from 150° F. to 250° F.

In certain embodiments, the production fluid may flow upward through thecoiled tubing 120 while it is cooled. Although this upward flow may beatypical, it is believed that this upward flow may be advantageous,particularly when the production fluid is a multiphase fluid. Bydirecting the flow upward, a multiphase flow regime will tend towardsslugging flow, which will continually move the gas along andintermittently wet inner surface 121 of coiled tubing 120. This may helpeliminate cold spots on inner surface 121 of coiled tubing 120 whichcould become nucleation sites for solid deposits such as paraffins.Also, the inner surface of coiled tubing 120 may warmed by the liquidflow allowing for a more uniform and efficient heat transfer. One ormore valves 160 may regulate the flow of production fluids through thehot production fluid line 127 and the vertical discharge line 128.

In certain embodiments, shroud 130 may be disposed around core 110 andcoiled tubing 120. In certain embodiments, shroud 130 may be a hollowstructure with generally cylindrical shape. Shroud 130 may beconstructed out of any material suitable for in a deepwater environment.Examples of suitable materials include steel, glass reinforced plastic,and various composite materials. In certain embodiments, shroud 130 maycomprise a coating 135. In certain embodiments, coating 135 may comprisea solid glass reinforced plastic, epoxy coatings, specialized paints,and a range of insulating materials. Coating 135 may be structural,semi-structural, or non-structural to achieve a desired shape, geometry,or surface characteristic. In certain embodiments, the shroud 130 may beheavily insulated so that during an unexpected shutdown, the warmedcooling fluid retained in the subsea production cooler module 101 willcool slowly to limit the formation of hydrates in the production fluids.

In certain embodiments, the thickness of coating 135 may be determinedby its desired properties. In certain embodiments, the coating may befrom about 0.005 inches thick to 0.020 inches thick. In otherembodiments, the coating may be from about from 0.1 inches thick to 0.4inches thick. In other embodiments, the coating may be from 0.02 inchesthick to 0.05 inches thick.

In certain embodiments shroud 130 may be sized to envelope the coiledtubing 120, with a clearance gap so it does not contact coiled tubing120, which may require the shroud internal dimensions and shape exceedthat of coiled tubing 120. In certain embodiments, shroud 130 may becylindrical with a diameter of between 3 feet and 15 feet and/or alength of between 10 feet to about 100 feet.

In certain embodiments, shroud 130 may comprise an inlet 131 and anoutlet 132. Inlet 131 may be located at the bottom of shroud 130 andoutlet 132 may be located near the top of shroud 130. In certainembodiments, inlet 131 may have a cross sectional area of from 10 squarefeet to 100 square feet. In other embodiments, inlet 131 may have across sectional area of from about 20 square feet to 50 square feet. Incertain embodiments, outlet 132 may be a single opening with a crosssectional area of from about 0.25 square feet to 20 square feet ormultiple openings having similar aggregate cross sectional area. Incertain embodiments, sea water or other cooling fluids may flow intoshroud 130 via inlet 131 and flow out of shroud 130 via outlet 132.

In certain embodiments, control valve 140 may regulate the flow of thesea water or other cooling fluid through outlet 132 of shroud 130. Incertain embodiments, the flow of sea water through shroud 130 may be aslow as 50 gallons per minute to as large as 3000 gallons per minute. Thesetting of control valve 140 may be adjusted to maintain a givenproduction fluid outlet temperature set point based upon production flowrate and inlet temperature. By manipulating control valve 140, anoperator, or a control system, can monitor and adjust the amount of heatbeing removed from the production stream to produce a desirable outlettemperature as well as purposefully halt the main process of heattransfer and retain the heat of the production stream in the cooler inthe event of an unexpected flow shutdown.

In certain embodiments, shroud 130 may further comprise one or moresupport structures 135. Support structure 135 may be located on a base136 of shroud 130. In certain embodiments, support structure 135 may beporous to allow the flow of cooling fluid into shroud 130, thus formingthe shroud inlet 131. Support structure 135 may be integral and anextension of the material used to construct the shroud 130, and maycomprise structural beams or other components that support shroud 130.Support structure 135 may be a separate component than shroud 130, andmay be permanently attached to shroud 130. Support structure 135 may beconstructed of different materials than shroud 130 and may be designedto provide a relatively heavy base to aid installation and may providehigh structural integrity at the base of the shroud to ensure itsrobustness.

In certain embodiments, shroud 130 may be removable. In certainembodiments, shroud 130 may comprise one or more lift points 137 whoseposition can be adjusted so that the net lift force vector passesthrough the center of gravity. In certain embodiments, shroud 130 may belifted upward from its normal position around core 110 and coiled tubing120. Once clear of the core 110, a robotic submarine (a RemotelyOperated Vehicle, or ROV) could inspect and/or test properties of anyexternal fouling present, and cleaning could be performed, either withtools attached to the ROV, or by a dedicated semi-automated walkingdevice similar to a swimming pool cleaner moving on or near the coils.

In certain embodiments, shroud 130 may comprise a conical roof 138. Theconical roof 138 may help to deflect falling sediment from entering thesubsea production cooler module 101 during non-operational periods.

The basic design of subsea production cooler module 101 creates a largeamount of pipe surface that is exposed to cold sea water or othercooling fluid. By encasing the coiled tubing 120 in a shroud 130, thevelocity at which the natural convection of the cooling fluid flowsaround the coiled tubing 120 may be increased, enhancing the heattransfer abilities of the subsea production cooler module 101.

During unplanned shutdowns, control valve 140 may be completely closedto trap warm sea water or other cooling fluid within subsea productioncooler module 101. The warmest cooling fluid may rise to the top ofsubsea production cooler module 101, potentially exposing the bottomportion of coiled tubing 120 to excessive cooling. In order to preventthe bottom coils from excessive cooling, subsea production cooler module101 may comprise an electric heater or a thermal reservoir 150, locatedbelow the lowest portion of the coiled tubing 120.

In certain embodiments, thermal reservoir 150 may comprise a storagetank 151, an inlet 152, an outlet 153, a valve 154, and coiled tubing155. Storage tank 151 may be capable of storing several hundred gallonsof warmed cooling fluid. In certain embodiments, storage tank 151 may bedisposed within a hollow center of core 110. In certain embodiments,storage tank 151 may be disposed in a cavity defined by coiled tubing120. In certain embodiments, storage tank 151 may be disposed in acavity defined by coiled tubing 155. In certain embodiments, coiledtubing 155 may be coiled around a bottom portion of core 110. Valve 154may regulate the flow of warmed cooling fluid through inlet 152, outlet153, and coils 155. In certain embodiments, coiled tubing 155 may havethe same material construction of coiled tubing 120.

During shutdowns, valve 154 may be opened to allow the warmed coolingfluid to flow through inlet 152, outlet 153, and coils 155. This warmedcooling fluid may heat the cooling fluid in the bottom portion of thesubsea production cooler module 101 and allow for the heating of thebottom portion of coiled tubing 120. In certain embodiments, storagetank 151 may comprise an expansion chamber 156 to allow for the warmedcooling fluid to swell and shrink, depending on its temperature. Duringnormal operation of the subsea production cooler module 101, the warmedcooling fluid in storage tank 151 may be warmed to the outlettemperature of the production fluid flowing through vertical dischargeline 128 by passage of the discharge line through the storage tank 151,allowing the contents to be heated by the production fluid until theirrespective temperatures are nearly the same.

In certain embodiments, subsea production module 101 may comprise arunning tool. The running tool may be a permanently-mounted or removablerunning tool. In certain embodiments, the running tool may be attachedto shroud 130. The running tool may allow for a true vertical removalpath for shroud 130 so that interference with the core 110 and coiledtubing 120 is minimized In certain embodiments, one or more centralizersmay ensure that the shroud does not contact coiled tubing 120 duringremoval or operation.

Referring now to FIG. 2, FIG. 2 illustrates a partial solid modelrendering of a subsea production cooler module 201 in accordance withcertain embodiments of the present disclosure. Similar to subseaproduction cooler module 101 illustrated in FIG. 1, subsea productioncooler module 201 may comprise a core 210, coiled tubing 220, and ashroud 230. In FIG. 2, coiled tubing 220 is shown to comprise fourindividual coils of tubing. Hot production fluid line 227 and verticaldischarge line 228 are shown to be within a hollow center of core 210.

Referring now to FIG. 3, FIG. 3 illustrates an alternative concept of asubsea prosecution cooler module 301. While in certain embodimentssubsea production cooler module 301 may share each of the same featuresof subsea production cooler modules 101 and 201, for example, subseaproduction cooler module 301 may comprise a core 310, coiled tubing 320comprising an inlet 325 connected to a hot production fluid line 327 andoutlet 326 connected to a vertical discharge line 328, one or morevalves 360, shroud 330 with an inlet 331 and an outlet 332, and acontrol valve 340, several key differences between subsea productioncooler module 301 and subsea production cooler modules 101 may exist.

One difference between subsea production module 301 and subseaproduction module 101, is that while the bottom of shroud 130 of subseaproduction cooler module 101 may be open to seawater, the bottom portionof shroud 330 is not open to seawater. Rather, shroud 330 completelyencases a bottom portion 315 of core 310 isolating it from contact withthe seawater. Instead, inlets 331 and outlet 332 of shroud 330 may befluidly connected to a cooling fluid chiller 370.

In certain embodiments, cooling fluid chiller 370 may surround a topportion 316 of core 310. In certain embodiments, cooling fluid chiller370 may comprise chiller tubing 371 and chiller shroud 376.

In certain embodiments, chiller tubing 371 may comprise the samefeatures of coiled tubing 120. In certain embodiments, chiller tubing371 may be coiled around a top portion 316 of core 310. In certainembodiments, chiller tubing 371 may comprise an inlet 372 and an outlet373. In certain embodiments, inlet 372 may be connected to outlet 332 ofshroud 330 by means of a warm coolant line 374. In certain embodiments,outlet 373 may be connected to inlet 331 of shroud 330 by means of acold coolant line 375. In certain embodiments, a coolant expansionchamber 356 may be connected to the cold coolant line 375.

In certain embodiments, chiller shroud 376 may be disposed around topportion 316 of core 310 and chiller tubing 371. In certain embodiments,chiller shroud 376 may share similar characteristics of shroud 130. Incertain embodiments, a valve 377 may regulate the flow of sea waterthrough inlet 378 and outlet 379 of chiller shroud 376.

In certain embodiments, chiller shroud 376 may further comprise one ormore support structures 380. Support structure 380 may be located on abase 381 of chiller shroud 376 and attach chiller shroud 376 to shroud330. In certain embodiments, support structure 380 may be porous toallow the flow of cooling fluid into chiller shroud 376, thus formingthe inlet 378. Support structure 380 may share common characteristicswith support structures 135.

During operation, warmed coolant from outlet 332 of shroud 330 may flowupward into chiller tubing 371 of cooling fluid chiller 370. The warmedcoolant may be cooled by surrounding sea water flowing into the chillershroud 376 through inlet 378. As the warmed coolant is cooled, it mayflow downward through chiller tubing 371 where it is further cooled byseawater flowing upward through chiller shroud 376. The cooled coolantmay then exit cooling fluid chiller 370 via cold coolant line 375 andre-enter the bottom of shroud 330. One or more valves 360 may regulatethe flow of cooling fluid through the warm coolant line 374 and the coldcoolant line 375 and one or more valves 340 may regulate the flow of seawater through inlet 378 and outlet 379.

Referring now to FIG. 4, FIG. 4 illustrates subsea production cooler 400comprising subsea production cooler modules 401, base 485, and pipingsystem 490.

Subsea production cooler modules 401 may comprise any of the componentsof subsea production cooler modules discussed previously.

Base 485 may be designed to contain piping system 490 and to provide oneor more sites 486 to install the one or more subsea production coolermodules 401. FIG. 4 illustrates a subsea production cooler comprising 4subsea production cooler modules 401 installed on base 485 with 5 sites486.

In certain embodiments base 485 may be constructed mainly of steel,similarly to other subsea equipment such as piping manifold, subseapumping systems, etc. The base 485 may be (when viewed from above)roughly 40 feet wide, 100 feet long, and 20 feet tall. The base 485 maybe set on the seafloor itself using a mudmat. The base 485 may be setonto one or more subsea pilings designed to resist not only the weightof the base, but also to predictably resist any moment created by therather tall subsea production cooler modules 401, or by uneven orimbalanced loading created by various combinations of filled or emptysites 486. In certain embodiments sites 486 may comprise a multiboreconnector. In certain embodiments, sites 486 may support the forces andmoments generated by the presence of subsea production cooler module 401via the multibore connector, or support for the subsea production coolermay be supported by contact of one or more structural members of thesubsea production cooler resting on the base 485. In certainembodiments, sites 486 may support the subsea production cooler module401 by a combination of the multibore connector and separate structuralmembers.

Piping system 490 may comprise a hot multiphase production line 491, aseparator 492, a hot gas line 493, a hot liquid line 494, a cooledliquid line 495, and a cooled multiphase production line 496. In certainembodiments, separator 492 may comprise an arrangement of pipingcomponents arranged so as to slow the multiphase mixture and allowgravity separation of liquids and gas, while simultaneously providingflowpaths for both liquid-rich streams and gas-rich streams. Separator492 may separate the fluid from hot multiphase production line 491 intohot gas line 493 and hot liquid line 494. At typical operatingcondition, when entering separator 492, the temperature of the fluid inhot multiphase production line 491 may be from 300° F. to 450° F., thepressure may be in the range of from 1500 psia to 7000 psia, and the gasvolume fraction may be in the range of from about 0% to about 80%. Theparticular operating conditions are dependent on the producing wells andthe manner in which the system is operated, and can vary considerably,so these parameters are intended only to illustrate, not to limit theoperational envelope of the system being described.

When exiting the separator, the fluid in hot liquid line 494 may bemostly liquid with a minor amount of gas. In certain embodiments, thefluid in hot liquid line 494 may have a gas volume fraction of fromabout 0% to about 10% at very nearly the same pressure and temperatureof the fluid in hot multiphase production line 491. In certainembodiments, the fluid in hot gas line 493 may be mostly gas with aminor amount of liquid. In certain embodiments, the fluid in hot gasline 493 may have a gas volume from of from 90% to about 100% at verynearly the same pressure and temperature of the fluid in hot multiphaseproduction line 491.

The flowrate of fluid in hot gas line 493 may controlled by flow controlvalve 497, that may simply match, or nearly match, the pressure dropcreated by various piping and subsea production cooler modules 401.Further, in certain embodiments, manipulation of the temperature offluid in cooled multiphase production line 496 in relation to thetemperature of the fluid in cooled liquid line 495 may be implemented byflow control valve 497. In certain embodiments, this control may beutilized to ensure that a certain thermal mass flowrate exists in hotgas line 493, so that in mixing with fluid in cool liquid 495, a certainhigher temperature is maintained in cooled multiphase production line496.

The fluid in hot liquid line 494 may flow into a single subseaproduction cooler module 401 or multiple subsea production coolermodules 401 arranged in series or in parallel. Cooled liquid line 495may be a single stream flowing from a subsea product production cooler,or multiple streams flowing from multiple coolers combined. Fluid fromcooled liquid line 495 may be combined with the fluid in hot gas line493 to form the cooled multiphase production line 496. The fluid incooled multiphase production line 496 may be nearly the same gas volumefraction as that in hot multiphase production line 491, or by effect ofthe cooling have attained a gas volume fraction of zero. The temperatureof fluid in cooled multiphase production line 496 may be between 150° F.and 300° F. The pressure of fluid in cooled multiphase production line496 may be near to, but somewhat less than the pressure in hotmultiphase production line 491, or it may be considerably lower due topressure drop in separator 492 and subsea production cooler modules 401.

In certain embodiments, the subsea production coolers discussed hereinmay have a wide range of operating conditions. In certain embodiments,an operator or a control system can monitor and adjust the amount ofheat being removed to produce a desirable outlet temperature as well aspurposefully halt the main process of heat transfer and retain the heatof the production in the cooler in the event of an unexpected flowshutdown. In certain embodiments, the subsea production coolersdiscussed herein are capable of cooling production streams utilizingnatural convection and do not require the pumping of cooling fluids.

While the embodiments are described with reference to variousimplementations and exploitations, it will be understood that theseembodiments are illustrative and that the scope of the inventive subjectmatter is not limited to them. Many variations, modifications, additionsand improvements are possible.

Plural instances may be provided for components, operations orstructures described herein as a single instance. In general, structuresand functionality presented as separate components in the exemplaryconfigurations may be implemented as a combined structure or component.Similarly, structures and functionality presented as a single componentmay be implemented as separate components. These and other variations,modifications, additions, and improvements may fall within the scope ofthe inventive subject matter.

1. A subsea production cooler module comprising: a core; a coiled tubingdisposed around the core, wherein the coiled tubing comprises an inletand an outlet; and a shroud at least partially encasing the core and thecoiled tubing.
 2. The subsea production cooler module of claim 1,further comprising a control valve at the top of the shroud capable ofregulating the flow of fluid through the shroud.
 3. The subseaproduction cooler module of claim 1, wherein the core and the shroud areinsulated.
 4. The subsea production cooler module of claim 1, whereinthe shroud comprises a conical roof.
 5. The subsea production coolermodule of claim 1, wherein the coiled tubing comprises an inner coatingand an outer coating.
 6. The subsea production cooler module of claim 1,wherein the coiled tubing comprises multiple coils of tubing in closeproximity to each other.
 7. The subsea production cooler module of claim1, wherein the coiled tubing comprises an inner coil and an outer coilspiraled around the core in opposite directions.
 8. The subseaproduction cooler module of claim 1, further comprising a thermalreservoir disposed in a cavity defined by the coiled tubing.
 9. Thesubsea production cooler module of claim 1, further comprising a coolingfluid chiller disposed about a top portion of the core.
 10. The subseaproduction cooler module of claim 9, wherein the fluid chiller comprisesa chiller tubing and a chiller shroud
 11. The subsea production coolermodule of claim 1, wherein the shroud is removable.
 12. A subseaproduction cooler comprising: a subsea production cooler module; whereinthe subsea production cooler module comprises: a core; a coiled tubingdisposed around the core, wherein the coiled tubing comprises an inletand an outlet; and a shroud at least partially encasing the core and thecoiled tubing; a base; and a piping system.
 13. The subsea productioncooler of claim 12, wherein the subsea production cooler comprisesmultiple subsea production cooler modules arranged in series.
 14. Thesubsea production cooler of claim 12, wherein the subsea productioncooler comprises multiple subsea production cooler modules arranged inparallel.
 15. The subsea production cooler module of claim 12, whereinthe piping system comprises a separator comprising a hot productionline, a hot liquid line, and a hot gas line comprising a flow controlvalve.
 16. A method of cooling a subsea production stream, the methodcomprising: providing a subsea production stream and cooling the subseaproduction stream with a subsea production cooler module, wherein thesubsea production cooler module comprises: a core; a coiled tubingdisposed around the core, wherein the coiled tubing comprises an inletand an outlet; and a shroud at least partially encasing the core and thecoiled tubing.
 17. The method of claim 16, wherein cooling the subseaproduction stream with the subsea production cooler module comprises:separating the subsea production stream into a hot liquid stream and ahot gas stream; cooling the hot liquid stream with the subsea productioncooler module thereby forming a cooled liquid stream; and combining thecooled liquid stream and the hot gas stream to form a cooled subseaproduction stream.
 18. The method of claim 16, wherein cooling thesubsea production stream with the subsea production cooler comprisesflowing the production stream upward through the coiled tubing.
 19. Themethod of claim 18, wherein cooling the subsea production stream withthe subsea production cooler further comprises allowing cooling fluid tonaturally convect within the shroud.
 20. The method of claim 19, whereincooling the subsea production stream with a subsea production cooler isperformed without pumping the subsea production stream or the coolingfluid.